A series of high molecular weight, unsymmetrically substituted poly(ferrocenylsilanes) [Fe-(eta-C5H4)2(SiRR’)]n (4a-4g) (a R = Me, R’ = H; b R = Me, R’ = CH2CH2CF3; c R = Me, R’ = CH=CH2; d R = Me, R’ = n-C18H37; e R = Me, R’ = Ph; f R = Me, R’ = Fc, Fc = (eta-C5H4)Fe(eta-C5H5); g R = Me, R’ = Nor, Nor = 5-norbornyl) have been prepared via the thermal ring-opening polymerization of the corresponding strained, silicon-bridged [l]ferrocenophanes Fe(eta-CrH4)2(SiRR’) (3a-3g). The latter species were prepared via the reaction of Fe(eta-C5H4Li)2.tmeda (tmeda = tetramethylethylenediamine) with the appropriate unsymmetrical dichloroorganosilane RR’SiCl2. The poly(ferrocenylsilanes) 4a-4g were structurally characterized by H-1, C-13, and Si-29 NMR spectroscopy and by elemental analysis. The molecular weights of polymers 4a-4g were estimated to be in the range M(w)BAR = 1.6 X 10(5)-2.7 X 10(6) and M(n)BAR = 7.1 X 10(4)-8.1 X 10(5) by GPC using polystyrene standards. In addition, the solution behavior of a moderate molecular weight sample of 4e was investigated by low-angle laser light scattering, which yielded an absolute value of M(w)BAR = 8.54 X 10(4) and a second virial coefficient A2 = 3.3 X 10(-4) mol cm2 g-2 in THF at 20-degrees-C. The thermal transition behavior of polymers 4a-4g was investigated by DSC. Glass transition temperatures were found to vary with the substituents at silicon and were in the range of 1-degrees-C (for 4d) to 99-degrees-C (for 4f). A strong melting endotherm for 4d at 16-degrees-C was detected by both DSC and DMA and annealed samples of 4a showed very weak melt endotherms at 87 and 102-degrees-C. None of the other polymers showed evidence for melting transitions. WAXS analysis confirmed that 4b-4g are essentially amorphous at 25-degrees-C whereas 4a is more ordered. The electrochemical behavior of 4a-4g was investigated by cyclic voltammetry, and 4a-4e and 4g showed two oxidation waves, which is consistent with the presence of significant interactions between the iron centers. The cyclic voltammogram of 4f was more complex and indicated that interactions exist between the iron centers in the polymer backbone and the ferrocenyl side groups.